This proposal requests support for a Keystone Symposia meeting entitled The Life of a Stem Cell: From Birth to Death, organized by Margaret A. Goodell, Ruth Lehmann and Thomas A. Rando, which will be held in Olympic Valley, California from March 11 - 16, 2012. Stem cell studies have demonstrated unexpected plasticity of cellular differentiation programs and challenged the long-standing paradigm of progressive irreversibility of cell fate during development. The field of stem cell biology interfaces with many areas of basic biology including developmental biology, tissue growth and homeostasis, regeneration, cancer and aging. Unlike most meetings on stem cells, the Keystone Symposia meeting on The Life of a Stem Cell: From Birth to Death focuses on stem cells within the context of the organism. Stem cell systems are discussed with respect to the life cycle of whole organisms: gametogenesis and embryogenesis, where tissue types are established; maturity, where organ systems are maintained in homeostasis; and aging, where stem cells systems change physiologically or because of disease. Speakers have been chosen to broadly reflect lessons learned from a variety of model organisms, experimental approaches and organ systems. PUBLIC HEALTH RELEVANCE: Stem cell biology is one of the most rapidly growing fields in modern biology. A better understanding of the biology of stem cells and their manipulation has generated new insight into the regenerative capacity of tissues and organs and has provided new understanding of the cellular mechanisms underlying diseases such as cancer and aging. The Keystone Symposia meeting on The Life of a Stem Cell: From Birth to Death will seek to address the gaps in knowledge regarding the major differences between different populations of stem cells and how their respective environments contribute to these functional differences.